1. Field of the Invention
This invention is concerned with a locking device for connecting a driveshaft to a power take-off shaft, the invention finding a particular use in connecting a driveshaft for driving an agricultural implement to the power take-off shaft of a tractor.
Such a locking device comprises a coupling sleeve mounted on the driveshaft and arranged to slide on to the power take-off shaft, the coupling sleeve defining a plurality of radially-extending apertures, a plurality of locking members guided in the apertures of the coupling sleeve for inward movement to lock the coupling sleeve against axial movement relative to the power take-off shaft and outward movement to allow such axial movement, a locking sleeve on the coupling sleeve which may be moved between a locking position thereof in which it embraces the locking members and prevents outward movement thereof and a release position thereof in which the locking sleeve allows outward movement of the locking members, resilient biasing means operable to bias the locking sleeve into its locking position, and latch means operable to hold the locking sleeve in its release position and releasable by outward movement of the locking members as the coupling sleeve is slid on to the power take-off shaft.
2. Description of Prior Art
In U.S. patent specification No. 4639163 (equivalent to West German No. 33 45 732) a locking device is proposed in which the latch means comprises an additional sleeve provided with locking hooks arranged within the locking sleeve. After reaching a certain point in the axial movement of the locking sleeve, the locking hooks engage the apertures in which the locking members are guided, thereby preventing the locking sleeve from returning to its locking position. Such a return of the locking sleeve into its locking position would prevent coupling of the driveshaft to the power take-off shaft. The disadvantage of the latch means described in the aforementioned U.S. patent specification lies in the necessity to provide a number of additional components to provide the latch means complicating the design and increasing the risk of dirt or corrosion leading to a malfunction.
It is an object of the present invention to provide a locking device which has a simple design, consists of only a few components, and operates efficiently.